The lawsuits, filed Thursday in Los Angeles County Superior Court, contend that “certain of Toyota’s cars and trucks have a defect that causes sudden uncontrolled acceleration to speeds of up to 100 mph or more.” The insurers cite data that blames 725 crashes on the problem and fault Toyota for failing to equip its cars with an override system that would cause a car to idle if the brake and gas were deployed simultaneously.

Toyota has contended that the acceleration problems were related to sticky gas pedals and bulky floor mats that could cause the pedals to stick, problems that the Japanese automaker said have been resolved through the recalls of millions of vehicles. It denies the allegation, contained in many pending lawsuits, that a problem in the cars’ electronic throttle control system causes the cars to unexpectedly accelerate.

Toyota issued a statement Monday that said the latest lawsuits are without merit, noting that such disputes “are common between insurers and automakers.”

“Toyota believes that any allegation that a vehicle-based defect is the cause of unintended acceleration in this or any other complaint is completely unfounded and has no basis,” said Toyota spokeswoman Celeste Migliore.

The insurers were represented by Howard Maycon and David Denton, from the Los Angeles offices of Cozen O’Connor. They could not be reached.

The wave of insurance company litigation comes nearly three months after Allstate Corp. sued Toyota to recover $3 million it paid to cover damages from 270 crashes. And it follows the recent disclosure that Toyota paid $10 million to resolve a lawsuit filed by the relatives of four people, including California Highway Patrol Officer Mark Saylor, who were killed in a fiery crash near San Diego in August 2009.

That accident was captured on a chilling 911 phone call and touched off a string of massive recalls, federal investigations and fines.

On top of the insurers’ lawsuits, Toyota faces dozens of lawsuits filed by relatives of people who were killed in crashes blamed on sudden acceleration and others who were injured in such accidents. The bulk of those cases have been consolidated before a federal judge in Santa Ana.

In addition, a class-action lawsuit, pending before the same judge, seeks damages on behalf of Toyota vehicle owners who say the value of their cars has diminished because of the alleged acceleration problems.

Attorneys suing Toyota Motor Corp. over sudden acceleration are building their cases around the automaker's resistance to installing a brake system that they claim would have prevented deaths and injuries. The emerging legal strategy is centered on Toyota's slow adoption of so-called brake override systems, which attorneys say is the automaker's single biggest vulnerability as it defends itself against more than 100 lawsuits in state and federal courts.